Contribution of Rhododendron eriocarpum Nakai to the flower color variation in R. sataense Nakai

The origin of flower color variation in R. sataense was discussed by means of the comparison of some morphological characteristics of flowers and petal pigmentation in R. sataense with those of R. eriocarpum, R. kaempferi and their F₁ progenies. Flower color variations were very wide in R. sataense, whereas those in the two other wild species were extremely narrow. Although there were no F₁ the individuals having vermilion or red flowers, the flower color variations of them were wider than those of R. eriocarpum. The frequency of individuals having 5 stamens were highest in R. sataense and the number of stamens of R. kaempferi and R. eriocarpum were only 5 and 10, respectively. The number of stamens in the F₁ was different in the cross combinations. Almost all individuals of R. eriocarpum contained a high ratio of methylated flavonols in their petals, whereas R. kaempferi contained few amount. However, there were two groups identified in the F₁ hybrids regarding to the constitutions of the flavonols in their petals; one group was formed with individuals containing high percentage of methylated flavonols and another containing low. From these findings, it was possibly suggested that the appearance of the progenies with wide flower color variations, 5 stamens and containing few methylated flavonols in their petals such as R. sataense were able to be obtained from the crossing between R. eriocarpum and R. kaempferi.